1. Field of the Invention
This invention relates to expandable downhole tubing. In particular, the invention relates to coupling or connecting expandable downhole tubing. One aspect of the invention relates to a method of locating a section of expandable tubing in a bore.
2. Description of the Related Art
Expandable tubing for use in downhole applications is useful as, for example, borehole liner or as a sandscreen support. In one application, a section of expandable tubing is positioned in an unlined section of bore intersecting a hydrocarbon-bearing formation, below an existing bore casing and bore liner. The tubing is then expanded, preferably into contact with the bore wall. The expanded liner supports the bore wall while allowing oil and gas to pass from the formation into the bore. In another application, an expandable well screen is provided, the screen comprising perforated filter sheets mounted on an expandable slotted carrier tube and within a coaxial expandable slotted protective tube. The well screen is expanded downhole to such a size that the protective tube can be set against the surrounding formation.
For locating expandable tubing in a bore it would be preferable to provide a secure connection between the upper end of the expandable tubing and the lower end of an existing bore liner; simply locating the tubing in the liner, with no mechanical connection therebetween, may result in an offset between the two, creating an irregularity on which tools may snag and an unwanted gap through which fluid may flow.
U.S. Pat. No. 3,353,599 discloses a method for securing ends of expandable liner to solid surrounding tubing by means of plastic impregnated glass filter mats. However, the applicant considers that this method would encounter many difficulties in this particular application due to, for example, contamination of the mats by the fluid in the bore and the possibility of the mats being dislodged or damaged during installation of the liner and the expandable tubing, or during other downhole operations.